1. Field of the Invention
The present invention relates to an uninterruptible duplexed power supply system for driving a load in accordance with the rectified output from a commercial alternating current (AC) power supply during normal operation, and for driving a load in accordance with output from a secondary battery or some other direct current (DC) power supply when a power outage or some other abnormality occurs, and more particularly to an uninterruptible duplexed power supply system, which is utilized to operate important equipment such as precision machinery and automated equipment for crime prevention, disaster prevention, telecommunications, information (servers, FA personal computers), and medical treatment. Here, power outage refers to an interruption in a supply of electric power (electric current), for example, when the power supply from an electric power company is interrupted, or when a power supply is interrupted by a circuit breaker opening, a plug coming out of a socket, or a wire breaking.
2. Description of the Related Art
Computer servers, in particular, are required to operate continuously 24-hours-a-day without stopping for five years. In general, the power supply system shown in FIG. 4, for example, is the specific configuration used therefor. This system is designed to enable power to be supplied to a load continuously, and constitutes an uninterruptible power supply (UPS) 50 connected to a commercial AC power supply; 2 switching power supplies 51, 52, which connect in parallel for securing (duplexing) the switching power supply used as the power supply for the server; and 2 sets of diodes 53, 54 for preventing sneak current, by which a current outputted from one switching power supply of these switching power supplies 51, 52 flows into the other switching power supply. Therefore, this system is constituted so that when one switching power supply 51 fails as a result of a lightning surge, or any of various impulse surges and the like being introduced into the AC line, the other switching power supply 52 is capable of supplying power to a load in its place.
According to the above-described constitution, because the switching power supplies 51, 52 are connected in series to the uninterruptible power supply 50, the 75-80% efficiency of the switching power supplies 51, 52 is crossed with the 75-80% efficiency of the uninterruptible power supply 50 to produce an approximately 55-64% overall efficiency, and is inexpedient in that energy loss becomes a problem.
Further, because the uninterruptible power supply 50 is separate from the 2 switching power supplies 51, 52, it is inexpedient in that not only is a large space required, but the price is also high.
Further, 2 diodes 53, 54 are required to prevent sneak current in the 2 switching power supplies 51, 52, respectively, requiring a total of 4 or more diodes in all, thus causing the system to become even larger.
The inventors previously proposed an apparatus for solving the above-mentioned inexpediencies. As disclosed in Japanese so Patent No. 2702048, this constitutes an uninterruptible switching regulator (uninterruptible duplexed power supply system), which integrates an AC power circuit, a DC power circuit, switching circuits relative thereto, and a secondary DC outputting circuit, which supplies electric power to a load, by connecting to the primary winding of a high-frequency transformer a power circuit comprising a rectifying circuit, which rectifies the AC from a commercial AC power supply, and a switching device provided on the output side of this rectifying circuit, and connecting to the secondary winding of the above-mentioned high-frequency transformer a secondary DC outputting circuit, which supplies electric power to a load, and connecting to the tertiary winding of the above-mentioned high-frequency transformer a DC power circuit, comprising a switching device and the like for operating this DC power circuit in accordance with the operating status of the above-mentioned power circuit.
However, when the above-mentioned power circuit malfunctions as a result of a lightning surge or any of various impulse surges being introduced into the AC input line, although a load can be driven in case of emergency by the DC power circuit, the damaged components of the power circuit must be replaced. During this replacement, the power supply must be shut OFF after using a predetermined operation to temporarily shut down the computer. Not only is this shutdown operation troublesome, but the computer cannot be operated during this replacement work. This system is thus inexpedient in that it does not fully satisfy the conditions of a stable, reliable power supply.
Further, structurally it was difficult to replace the damaged components of the above-mentioned power circuit while the DC power circuit was driving a load.
Consequently, up until now, it has been necessary to use a method, wherein the above-described uninterruptible switching regulator (uninterruptible duplexed power supply system) is connected in parallel just like the switching power supplies 51 and 52 of FIG. 4. Moreover, because a parallel connection is used, the diodes 53, 54 of FIG. 4 are necessary to prevent sneak current, with the result that, to the extent that the uninterruptible power supply, (UPS) 50 became unnecessary, the system was unsatisfactory from the standpoint of achieving compactness and conserving space, and was uneconomical.